Heat sealable padding materials are known. For example, thermoplastics are employed as heat-seal adhesives for planar textile materials. Thermoplastic heat-seal adhesives are applied by wiping thickened pastes or solutions of the adhesive onto the textile, or by sprinkling pourable adhesive powders onto the textile. Moreover, it is also known to spray dispersions or solutions of the adhesive onto the fabric, or to apply the adhesive in the form of a spunbonded fabric. Heat seal adhesives should not adversely affect the soft feel of the textile, and the bonds formed should be resistant to chemical cleaning and washing.
A preferred method for the manufacture of heat-sealable padding materials comprises coating a planar textile fabric, such as the spunbonded fabrics with a heat-seal adhesive. For example, the adhesive may be in paste form, and may be applied to the planar textile material by a paste printing machine and a rotary stencil. The printed padding material is bonded to a second fabric material, by pressing the two textiles together under heat and pressure - for example, by hot-ironing the fabrics.
Plastics suitable for use as heat-seal adhesives are known. For example, polyethylenes which soften or melt at temperatures of from about 90.degree. C. to about 130.degree. C. are suitable for use as heat-seal adhesives. However, bonds formed from polyethylene heat-seal adhesives do not stand up well to cleaning with chemical cleaning agents such as perchloroethylene, since the polyethylenes are soluble in perchloroethylene, and swell in the presence of perchloroethylene. Thus, during cleaning a polyethylene adhesive may separate from the substrate fabric to which it was previously bonded. Moreover, the resistance of polyethylene adhesives to washing with conventional detergents is not always adequate.
Soft, powdered polyvinylchloride has also been employed as a heat-seal adhesive. However, plasticizers must be added to printing pastes prepared from polyvinylchloride adhesives. These plasticizers are volatile at the temperatures employed during the ironing or sintering process. Thus, the use of polyvinylchloride pastes results in a hardening of the textiles to which the adhesive is applied. Moreover, textiles to which polyvinylchloride pastes have been applied may also harden gradually at room temperature. For the same reasons, mixed polyvinylchloride-polyvinylacetate polymers which require large amounts of plasticizers when employed as hot adhesives may be considered unsuitable for use in many cases.
Polyurethane, heat-seal adhesives useful for cementing together textile fabrics are described in German Pat. No. 1,930,340 and DE-OS 1769-482. The polyurethanes described in these references have good adhesive strength. However, they are relatively hard and, therefore, padding material which has been coated with these polyurethane adhesives, after being cemented to one outer layer of fabric material, results in a fabric product having an undesirable, hard or stiff feel. This same hard or stiff feel is produced when polyamide heat-seal adhesives are employed.
The polyurethanes disclosed in the above-cited German Pat. No. 1,930,340 may be applied in the form of a printable paste, or may be sprinkled onto the textile by the powder-sprinkling method or the powder-dot method. However, prior to their use as heat-seal adhesives they must be comminuted. This necessitates an expensive milling process which results in granulate polyurethane having a particle size in the range of from 1 to 80 .mu.m. Due to the intense heat produced during the milling step, the granulate must be cooled. This cooling may be accomplished with liquid nitrogen. The polyurethane particles produced by this process have a very non-uniform morphology. Thus, in light of the disadvantages associated with the polyurethane adhesives disclosed by the cited reference, the usefulness of these polyurethanes is limited--despite their basically good adhesive properties.